$REAL_USER_ID

IO::Handle->output_field_separator( EXPR )

${^OPEN} An internal variable used by PerlIO. A string in two parts, separated by a \0 byte

$UID

$^F The maximum system file descriptor, ordinarily 2. System file descriptors are passed to

$, The output field separator for the print operator. If defined, this value is printed between each of print's arguments. Default is

%OS_ERROR

$EXTENDED_OS_ERROR

$SYSTEM_FD_MAX

@ARGV The array @ARGV contains the command-line arguments intended for the script.